Arugula in Zone 6A — Great Plains

Arugula is a fantastic addition to any Great Plains garden. Its peppery leaves add a unique flavor to salads and sandwiches, and it thrives in our intense sunshine. Plus, it's incredibly versatile – you can harvest it young for a mild taste or let it mature for a bolder bite.

Our region is known for its extreme weather, including temperature swings and occasional hail, but arugula's quick growth cycle makes it a manageable crop for our 188-day growing season. With careful timing, you can enjoy fresh arugula from spring through fall.

Starting arugula indoors is an option, especially if you're eager for an extra-early harvest. Aim to start your seeds indoors from early to late March, about three weeks before you plan to transplant them. Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light – a sunny windowsill or under grow lights works well.

Bottom watering helps prevent damping-off, a common problem with seedlings. Honestly, though, arugula is so easy to direct sow that starting indoors is usually only worth it if you're trying to get a jump start in a particularly cool spring.

Transplant your arugula seedlings outdoors from early April through mid May, once the soil has warmed up a bit. Be sure to harden them off first by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature fluctuations that are common in the Plains.

Space the seedlings about 6 inches apart. Keep an eye on the weather forecast – a late frost can still happen in early April, so be prepared to cover your transplants if needed.

Direct sowing is the easiest way to grow arugula in the Great Plains. You can sow seeds from mid March through late August, giving you multiple harvests throughout the growing season. Arugula germinates best in cool soil, so spring and fall plantings are ideal.

Prepare your soil by loosening it and removing any rocks or debris. Sow seeds about ¼ inch deep and 6 inches apart. Keep the soil consistently moist until the seedlings emerge. The biggest challenge with direct sowing is that arugula tends to bolt (go to seed) in hot weather, so time your plantings accordingly.

Consistent watering is key to growing healthy arugula in our variable Great Plains climate. While arugula isn't drought-tolerant, overwatering can be just as detrimental. Aim to keep the soil consistently moist, but not waterlogged.

In the spring and fall, when temperatures are cooler and rainfall is more frequent, you might only need to water once or twice a week. During the hot summer months, you'll likely need to water more often, possibly every other day, especially if rainfall is scarce. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week, either from rain or irrigation.

Water at the base of the plants to avoid wetting the leaves, which can increase the risk of disease in our low-to-moderate humidity. Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch, like straw or wood chips, can help retain moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

You can expect your first arugula harvest about 40 days after planting, meaning anywhere from late April through late October, depending on when you sow. The leaves are ready to harvest when they're about 2-3 inches long. Smaller leaves have a milder flavor, while larger leaves have a more peppery taste.

To harvest, simply snip off the outer leaves with scissors or a knife, leaving the inner leaves to continue growing. This allows for continuous harvest throughout the season. Be sure to harvest before the plants start to flower, as the leaves will become bitter once they bolt.

As the first frost approaches in mid- October, you can extend your harvest by covering the plants with a row cover or bringing them indoors to a protected location.

Here are some common problems you might encounter growing arugula in the Great Plains:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You might also see small, dark beetles that jump when disturbed.
• What causes it: Small jumping beetles that feed on leaves. They're most damaging to small, young plants, and our dry springs can stress seedlings, making them more vulnerable.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. You can also delay planting until plants are larger and more resistant. Kaolin clay coating or neem oil spray can help deter the beetles. Interplanting with basil or catnip may also help.

Bolting in Heat

• What it looks like: The arugula plant sends up a flower stalk, and the leaves become tough and bitter.
• What causes it: Extended warm temperatures above the crop's comfort zone. Arugula bolts when days consistently exceed 80°F. This is a common problem in the Plains, where we can have sudden heat waves.
• How to fix/prevent it: Time your plantings for cool weather (spring and fall). Choose bolt-resistant varieties if available. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest frequently to encourage new growth and delay bolting.

Aphids

• What it looks like: Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. You might also see sticky honeydew residue or curled/distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. They're attracted to stressed plants, and our variable rainfall can sometimes lead to nutrient imbalances that weaken plants.
• How to fix/prevent it: Knock aphids off with a strong water spray. Encourage ladybugs and lacewings (natural predators). Insecticidal soap can be used for heavy infestations. Neem oil also works systemically. Avoid excess nitrogen fertilizer, as it attracts aphids.

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: Oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. While our humidity is generally low, periods of rain followed by warm days can create favorable conditions.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation around plants. Water at the base, never overhead. Copper-based fungicides can be used for prevention. Plant resistant varieties where available.

Great Plains Specific Challenges: The combination of hot summers, low-to-moderate humidity, and variable rainfall in the Great Plains presents unique challenges for growing arugula. The heat can cause bolting, while the variable rainfall can make it difficult to maintain consistent soil moisture. Wind protection is also essential, as strong winds can damage the delicate leaves.

Arugula benefits from companion planting. Lettuce and spinach make good companions because they share similar growing requirements and can provide shade for each other during hot weather. Carrots and beets help loosen the soil, which improves drainage for arugula. Onions deter pests like aphids.

Avoid planting arugula near strawberries. Strawberries are susceptible to verticillium wilt, a soilborne disease that can also affect arugula.